24 ROBERTS RUGH 



TABLE V 



Effect of Fetal X-Irradiation on Mouse Eyes ' 

 (Measurements at 6 weeks of age) 



Average diameter (in mm) '' Relative volume (%) 



Controls 3.555 100 



150 r at 12.5 days gestation 2.970 69.6 



250 r at 12.5 days gestation 2.670 50.6 



" X-irradiatioii f>f tlic developing mouse embryo seems to result in cellular deficiencies because tlic 

 damaged cells aie removed. When these ii radiations occur early, before the development of a specific 

 organ system, the deficiency resulting from the elimination of the necrotized cells results in a reduction 

 of organ size. The data of Table IV show that uith increasing irradiation at 12.5 days, there is a 

 decrease in the relative volume of the diameters of the mouse eyes at 6 weeks of age. An exposure of 

 250 r reduced the volume to approximately 50'J^. There are no studies thus far relative to the visual 

 acuity of these eyes. 



'' Minimum of 8 diameters of fixed eyes taken foi each a\eiage. 



Summary 



The early embryo is more radiosensitive than is the organism at any other 

 time in its entire life cycle. The earlier the stage, the more sensitive, with re- 

 gard to both survival and the development of anomalies. 



At the cellular level, there is no such thing as "recovery" from irradiation 

 damage, meaning a return to the preirradiated state. Since embryonic cells 

 are precursors of all cells of the adult, irreparable damage to surviving cells 

 results in such damage to all descendant cells of the adult organism. Ionizing 

 radiations represent a very potent tool. 



Figs. 36-43 are on pages 22 and 23. 



Fig. 36. When mouse embryos at 6.5 days are exposed to x-rays, 24 hours thereafter 

 they show the sloughing off of cells into the central cavity as seen here. The inner 

 neurectoderm will be deficient to the extent of this cellular loss. 



Fig. 37. This shows the neural groove at the level of the brain of 8.5-day embryos 

 24 hours after exposure to x-rays. Note the many pyknotic nuclei and the sloughed off 

 cells into the neural groove. 



Fig. 38. This is similar to Fig. 37 except it is at the level of somites. 



Fig. 39. In this figure note the many phagocytes posterior to the developing retina, 

 each of which contains a number of necrotic neurectoderm cells. This occurs about 

 24 hours after x-irradiation, but the retina will be deficient to the extent of this 

 cellular loss. 



Fig. 40. This is an enlarged view of the retina 4 hours after irradiation, showing 

 many pykotic nuclei. 



Fig. 41. This is an enlarged view of single phagocyte containing 14 dead neurecto- 

 derm cells from the x-irradiated retina. 



Figs. 42 and 43. These are enlarged views of the retina of the control Fig. 42 and 

 the irradiated Fig. 43 to show slight thinning of the various layers in the x-irradiated 

 eye of the mouse. 



